DESCRIPTION: This proposal is composed of three specific aims. The first is to determine whether the distribution and subtype composition of nicotinic and muscarinic receptors expressed by neuronal elements of Leopard frog tectum differs between mature and developing animals. This aim will employ receptor binding and immunocytochemistry in normal and surgically manipulated frogs. The second aim is to study the functional consequences of muscarinic and nicotinic receptor activation, specifically with regard to retinotectal transmission. These studies utilize patch-clamp techniques in brain slice preparations. The third aim will determine whether activation of nicotinic and muscarinic receptors is involved in the activity-dependent ordering of visual connections. These experiments involve chronically exposing a central visual target to cholinergic agonists and antagonists and then assessing the retinotopic order of its connections.